Excel 2007 :: How To Add Date Of Last Modification Of File To Printed Pages

We are using Excel 2007.

I wanted to add the date of the last modification of the file to the printed pages, so I googled how to do it and found a useful answer on this from from 10 years ago. It said to press ALT+F11, then on the left side go under VBAProject, there go to ThisWorkbook and there paste the next code:

Code:

Private Sub Workbook_BeforePrint(Cancel As Boolean)
For Each wk In Worksheets
With ActiveSheet.PageSetup
.LeftHeader = "Last Modified on " & ActiveWorkbook.BuiltinDocumentProperties.Item("Last Save Time")
.CenterHeader = ""

[Code]....

Then I saved it and closed. Like I said, it worked perfectly.

The problem is that when I open the file after closing it, it does not appear, and I have to paste the code again every time I open it. Not only is this not comfortable, it also counts as a modification, so even if I haven't changed the work sheets themselves, just wanted to open and print it, it shows today's date.

My question is, who to I save it permanently so it will remain always after the first time I created it?

While we're at it, if there's a way for that code to appear on every NEW Excel file I create automatically